British Empire, overseas territories linked to Great Britain in a variety of constitutional relationships, established over a period of three centuries. The establishment of the empire resulted primarily from commercial and political motives and emigration movements (seeimperialism); its long endurance resulted from British command of the seas and preeminence in international commerce, and from the flexibility of British rule. At its height in the late 19th and early 20th cent., the empire included territories on all continents, comprising about one quarter of the world's population and area.
